Mapeamento de Digitaria insularis ((l.) Fedde) resistente a inibidores de ACcase e EPSPS na região Médio-Norte Mato-grossense

Abstract

The last report of multiple resistance of Digitaria insularis (sourgrass) to EPSPs and the enzyme acetyl coenzyme A carboxylase’s (ACCase) inhibitors occurred in Mato Grosso in 2020, which demonstrated the necessity for a resistant monitoring toward this mechanism of action. The aim was to identify the occurence of resistant biotypes of this specie upon the graminicides herbicides and glyphosate in the Mato Grosso’s North Region. For this reason, seeds of sourgrass plants were collected from soybean fields in seven cities of the region (Cláudia, Santa Carmem, Sinop, Lucas do Rio Verde, Ipiranga do Norte, Sorriso and União do Sul). Then, screening trials were performed to evaluate potential resistant biotypes with application of the recommended average rates of clethodim (108 g ai ha-1 + 0,5% v/v oil mineral), fenoxaprop-p-ethyl (110 g ai ha-1 ), glyphosate (1.440 g ae ha-1 ) e haloxyfop-p-methyl (60 g ae ha-1 + 0,5% v/v oil mineral) and a control, with eight replications. At 28 days after the application (DAA), the percent of the visual control was analyzed, in which 0% correspond to no damage and 100% to plant death, and the biotypes were rated as susceptible, resistance or intermediary resistance. After, dose-response curve experiments were performed to 11 biotypes resistants suspects to glyphosate and two susceptible biotypes, along the application of ten rates of glyphosate (0D; 0,0625D 0,125D; 0,25D; 0,5D; 1D; 2D; 4D; 8D; 16D, in which D correspond to 1.440 g ae ha-1 ), and six replications, the percent of the visual control was evaluated, and residual dry matter was collected 28 (DAA). The data obtained from the experiments of dose-response curve was submitted to analysis of variance F test and the sigmoidal log-logistic regression model. Later, the doses required of control (DL) was calculated, also the reduction of dry matter (GR) of 50% and 80%, and the resistance factor (RF= GR50resistant/GR50susceptible). To the graminicides herbicides was not found suspects biotypes of resistance, The glyphosate resistance was confirmed for seven biotypes, with resistance factor between 0,85 untill 58,32. Therefore, that graminicides demonstrated efficacy at controlling the populations of Digitaria insularis, while the glyphosate can not be effective in the control in some areas in the Northern of Mato Grosso.